New Beam Position Monitors for the CERN LINAC3 to LEIR Ion Beam Transfer Line

The ion injection line into the CERN Low Energy Ion Ring (LEIR) has recently been equipped with nine, new, electrostatic Beam Position Monitors (BPMs) in order to measure and optimize the trajectory of the low intensity ion beams coming from LINAC3. In this paper, we describe the design of the BPM, the low noise charge amplifier mounted directly on the BPM, and the digital acquisition system. There is special emphasis on the first commissioning results where the measured beam positions were seen to be perturbed by EMI and charging of the BPM electrodes by secondary particles. The effect of mitigation measures, including repelling voltages on the electrodes and external magnetic fields, are also discussed.